1. Field of the Invention
The present invention relates to a polyorgnosiloxane having a specific structure containing a hydrophilic group and to a cosmetic containing it, that is, to a polyorganosiloxane with excellent emulsion stability and powder dispersibility and to a cosmetic containing it.
2. Description of the Related Art
A silicone oil is used as an oil component in many applications because of its harmlessness and so on. It is widely used in a cosmetic as well; especially a low-viscosity silicone oil having viscosity of 100 mm2/second or less is widely used in applications such as, for example, skin care and make-up, because of its excellent spreading properties, freshness, and harmlessness.
In the field of a cosmetic and the like, a silicone oil is generally used as emulsion; in that case, a silicone surfactant is used in many cases. As the silicone surfactant, a polyether-modified silicone having a polyoxyalkylene group in the siloxane's terminal or side chain has been known (see for example, Japanese Patent Publication No. H04-15762, Japanese Patent Publication No. H04-20407, Japanese Patent Publication No. H05-13126, Japanese Patent Publication No. H06-62385, Japanese Patent Publication No. H05-12979). In addition, a polyether-modified silicone whose main chain siloxane moiety is branched, disclosed in Japanese Patent No. 3724988,
and an ABA-type copolymer, as shown in the following formula (5) disclosed in Japanese Patent Laid-Open Publication No. 2005-154736, have been known as well.
(Wherein, Rb represents a linear or a branched alkylene group having 1 to 12 carbon atoms, or a phenyl group, wherein lb represents 1 to 5, mb represents 40 to 90, and nb represents 10 to 40. Xb represents an arbitrary bonding group, such as a urethane group, a urea group, an amide group, an ester group, and an alkyl ether group.)
As other hydrophilic groups, (poly)glycerine-modified silicones, such as a silicone having a (poly)glycerine group in Japanese Patent Publication No. S62-34039, a silicone having a branched siloxane moiety in Japanese Patent No. 3976226, and an ABA-type copolymer as shown in the following formula (6) in Japanese Patent Laid-Open Publication No. 2006-218472, have been known. These silicones have been known also as a powder-dispersion stabilizer of a powder-containing cosmetic.
(Wherein, R1b represents a linear or a branched alkyl group having 1 to 12 carbon atoms or a phenyl group, wherein mb′ to 120 and nb′ represents 1 to 11. R2b is exemplified by an alkylene group having 2 to 11 carbon atoms.)
A silicone surfactant with a different hydrophilic group, bonding position, hydrophilic-hydrophobic (silicone), and so on, is used depending on its use purpose; in particular, an ABA-type copolymer (a silicone-hydrophilic group-silicone type copolymer) has excellent stability for the use in an emulsion cosmetic and a powder-containing cosmetic.
However, the forgoing silicones used as an emulsifying agent and a powder-dispersion stabilizer could not achieve adequate skin affinity and cosmetic durability; thus, a silicone capable of achieving sufficient skin affinity and cosmetic durability, in addition to emulsion stability and powder-dispersion stability, has been desired.